Consider the following puzzle, borrowed from Nobel-prize winner Daniel Kahneman's Thinking, Fast And Slow:

    A bat and ball cost $1.10.

    The bat costs one dollar more than the ball.

    How much does the ball cost?

The puzzle naturally evokes an intuitive answer: 10 cents (the correct answer is 5 cents). The puzzle is a very simple math puzzle that is easily solved using careful reasoning. But when we are intellectually lazy, we tend to follow our gut instincts or intuitions, even when the task is not the kind of task that should be handled in this way. Mathematical and logical exercises typically cannot be solved using our gut instinct.

Daniel Kahneman and his colleague Amos Tversky, however, have taken this insight one step further. They have argued that we do not reason rationally in everyday circumstances and regularly are subject to cognitive illusions, produced by heuristics, or rules of thumb, that we rely on when we reason fast. The mistake we make in these cases is to rely on intuition-based decision making processes rather than slow conscious and careful reasoning. Only the latter type of cognitive processing is reliable as a method for making decisions and predictions. Or so the argument goes.

This, however, is not quite right. Most problems we face in everyday situations are not mathematical or logical in nature. Here are three examples. People who catch balls, such as outfielders in baseball, behave as if they solve “a set of differential equations in predicting the trajectory of the ball” (Dawkins). However, research has shown that outfielders do not engage in mathematical calculations of the trajectory of the ball (Brogaard & Marlow). Catching the ball is not possible on the basis of slow conscious reasoning. So, how do outfielders catch the ball? The answer is that they rely on something called a “gaze heuristic” (Gigerenzer). The brain does not bother calculating any real facts about the speed or trajectory of the ball. Instead, it uses an algorithm that adjusts the outfielder’s running speed so that the ball appears continually to move in a straight line in his field of vision. In other words, through practice, the outfielder’s brain has developed its own algorithm to make it possible for him to catch the ball.